Electric valve



April 7, 1936.. L. R. LUDWIG 2,036,27

ELECTRIC VALVE Filed July 19, 1934 2 Sheets-Sheet l INVENTOR WITNESSES L. R. LUDWHG ELECTRIC VALVE Filed July 19, 1954 2 Sheets-Sheet 2 INVENTOR leon/audw/g ATTORNEY Patented Apr. 7, 1936 PATENT OFFICE ELECTRIC VALVE Leon R. Ludwig, Wilkinsburg, Pa., assignor to Westinghouse Electric &- Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 19,

7 Claims.

My invention relates to an electric valve and particularly to a valve element for securing an improvement in transition commutation.

In the operation of vapor electric devices the current carried by any valve terminates in a steep-1y dropping wave form and the inverse potential is applied to the valve almost immediately after termination of the current carrying arc. While the insulatingqualities of the arc space rapidly increase after the termination of the current carrying are, it frequently happens that the insulation characteristic is not sufficiently restored to withstand the suddenly applied inverse potential.

It is, therefore, found that vapor electric rectifiers frequently suffer from an inverse current are at the moment of transition from the conducting to the non-conducting state.

It is an object of my invention to provide a vapor electric valve having means for increasing the time available for the building up of the insulating characteristic of the are space.

According to my invention, each Valve of an electric converter comprises parallel discharge paths, one of which carries the arc discharge throughout the greater portion of the current carrying period after which the arc is transferred to the parallel arc path allowing the first arc path to become deionized and consequently have a high insulating characteristic.

Preferably the second arc path carries current for such a short period of time that deionization after current zero will be very rapid.

I have also found that my improved valve may be utilized to terminate an arc before the normal current zero by inserting a suitable energy storage device such as a capacitor, in series with the second arc path. By suitable control the arc may be transferred to the secondary arc path at any desired time and the secondary arc will carry current until the storage device is completely charged, when the arc will be extinguished; if the time of charging of the storage device is sui'ficiently long to permit the deionization of the first arc path the arc will be completely extinguished.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the ac.- companying drawings, in which:

Figure l is a schematic illustration of the vapor electric valve embodying my invention;

Fig. 2 is a view similar to Fig. l but showing other means for controlling the transfer of the 1934, Serial No. 736,011

conducting are from the main to the auxiliary arc path;

Fig. 3 is a modification of my invention having the parallel arc paths in a common container;

Fig. 4 is a modification similar to Fig. 3 showing further means of controlling the transfer of the current carrying arc; and

Fig. 5 is a modification having a plurality of cathodes instead of a plurality of anode elements to provide the auxiliary arc path. The valve l according to my invention, comprises a main arc space 2 and an auxiliary arc space 3 connecting an alternating-current circuit l and a direct-current circuit 5.

According to the form of my invention illustrated in Fig. 1, each of the arc spaces of the valve l are in separate arc chambers 6, 1, both of the arc chambers being provided with a simple anode H), II, connected directly to the alternating-current circuit 4, and a vaporizable cathode l2, l3, directly connected to the directcurrent circuit 5. A suitable control device such as a make-alive electrode [5, is provided in the main discharge device 6 and suitable control means such as a unidirectional conductor I6 is provided for initiating the current carrying arc in the main arc chamber 6. The auxiliary discharge device 1 is also provided with a suitable control element such as make-alive electrode l8, which, in turn, is controlled through a suitable control element such as a grid-controlled auxiliary rectifier [9. For simplicity of illustration, I have shown the auxiliary control circuits I5, I6 and l8, l9 supplied directly from the alternating-current source 4, but it is understood that any suitable source of control potential may be utilized. V

, In the operation of my improved valve element, the unidirectional conductor It in series with the make-alive element l5 in the main discharge path 2, will break down upon the application of positive potential to the anode of the main discharge chamber 6 and pass a make- .alive current which initiates a cathode spot and .thereby initiates a main current carrying discharge in that element of the valve.

The auxiliary discharge path 3 is maintained in a blocked condition by means of a suitable grid control 20 applied to the auxiliary discharge device |9 connected in series with its make-alive electrode I8. Near the termination of the current carrying period, the grid control .mechanism 20 operates to release the auxiliary control tube IS in series with the make alive element l8 of the secondary arc path 3 and permits the establishment of a current carrying arc in the auxiliary arc path 3.

Any suitable means may be utilized for transferring the are from the main discharge path 2 to the auxiliary discharge path 3. However, this is most easily accomplished by inserting an additional voltage 2| between the anodes of the main and the auxiliary discharge path so that a greater potential is applied to the auxiliary discharge path 3.

When the current carrying discharge is transferred to the auxiliary path 3 there is substantially no inverse potential on the main discharge path 2 which will rapidly deionize and regain its insulating properties. The grid control mechanism is set to operate so near the end of the current carrying period that the auxiliary discharge path 3 carries current for only a very short period of time. This short discharge period will not heat up the mechanical parts of the auxiliary chamber or produce an unnecessary amount of ionized vapor in the arc space 3 of the auxiliary discharge device I. Consequently, its deionization and the restoration of its insulating properties will occur Within an extremely short period of time so that the application of the inverse potential is applied to a valve having a high insulating characteristic as regards to the inverse potential.

In the modification according to Fig. 2, the control of the auxiliary discharge path 3 is effected by means of a current transformer in the anode lead of the main discharge path 2. Near the termination of the conducting period in the main discharge device, the current through the valve has a rapidly drooping characteristic. This rapidly drooping characteristic actuates the current transformer 25 to provide a positive impulse and release the grid-controlled tube i9 of the make-alive electrode [8 in the auxiliary discharge path 3. In this modification I have illustrated the auxiliary discharge path 3 as a device having a lower arc drop than the main discharge path 2.

In general, it has been found that it is possible to make very small make-alive type valve elements having a lower arc drop than similar elements of a larger size. This difference in arc drop is sufiicient to transfer the conducting are from the main arc path 2 to the auxiliary arc path 3. Also it is possible to construct hot cathode devices having suificient current carrying capacity to carry the tail end of the current carrying arc of a vapor electric device without unduly shortening the life of the hot cathode device. The use of such hot cathode devices instead of a smaller make-alive type valve element is contemplated as a part of my invention.

In the modification according to Fig. 3, the main and auxiliary arc paths are placed within a single valve chamber 30, a suitable control electrode 3i being associated with the auxiliary arc path 3 to prevent striking until the desired time interval. In the operation of this modification, suitable control devices such as a makealive electrode [5 and its associated valve element l6 may be utilized for initiating the main discharge arc. The auxiliary arc path is blocked by a suitable control electrode as, for instance, a grid 3|, which is maintained at a negative potential by means of a suitable bias 32. A suitable control device 33 is utilized to supply a positive impulse for releasing the control electrode '31 when it is desired to transfer the current carrying are from the main arc path to the auxiliary arc path. A suitable potential 2| is preferably inserted between the main and auxiliary arc paths to insure the transfer of the are from the main to the auxiliary arc path.

The modification according to Fig. 4 is similar to that of Fig. 3, except that the control grid 3| of the auxiliary arc path is controlled by means of a current transformer responsive to the decrease in current near the termination of the conducting period of the valve.

The valve element according to Fig. 5 difiers from the preceding modifications in that the main and auxiliary arc paths are provided between main and auxiliary cathodes instead of between main and auxiliary anodes. The auxiliary cathode is provided in the form of a grid element 40 spaced from the anode Ill and main cathode l2 in such a manner that the main are from the anode II] to the main cathode E2 must flow through the auxiliary cathode element 40.

In the operation of this device, suitable control apparatus is actuated to initiate the main current carrying arc to the main cathode l2. Near the termination of the current carrying period a suitable make-alive device 4| is used to strike a cathode spot on the auxiliary gridlike cathode 40. Since the arc drop between the grid-like cathode 40 and the main cathode 42 are materially different, the arc will immediately transfer to the auxiliary cathode 40, thus extinguishing the main cathode spot and permitting deionization of that portion of the arc space between the main cathode l2 and the auxiliary cathode 40.

The improved valve element according to my invention, has a further advantage in that the transfer of the current carrying are from the main to the auxiliary arc may be utilized to terminate a current carrying arc prior to normal current zero. By connecting a suitable capacitor 45 in the auxiliary arc circuit, the current carrying are when transferred from the main to the auxiliary circuit will charge the capacitor 45, and when the capacitor is fully charged, the current in the auxiliary arc path will terminate. The capacitor 45 must have sufficient capacity so that the time of receiving a charge is suificient to permit suflicient deionization of the main arc path, in order to prevent restriking of the main arc path.

When the capacitor 45 is connected as shown in Fig. 5, it will discharge through the main are at the next conducting period, and thus be ready to again interrupt the current at the end of the conducting time interval, but if the capacitor 45 is inserted in series with the auxiliary arc paths as illustrated in Figs. 1 to 4, a discharging means such as a resistor in shunt with the capacitor must be used.

While I have shown and described specific embodiments of my invention, it will be apparent to those skilled in the art that many changes and modifications can be made therein without departing from the true spirit of my invention or the scope of the accompanying claims.

I claim as my invention:

1. An electric converter comprising a cathode, a pair of parallel connected anodes cooperating with said cathode, a grid associated with one of said anodes for controlling the formation of a current carrying arc thereto and means for impressing'a higher voltage on said controlled anode than on said first-mentioned anode.

2. An electric converter element comprising two parallel arc paths, means for initiating current flow through one of said are paths, means for blocking the parallel arc path and means responsive to decrease of current through the first arc path for releasing said parallel arc path and means for transferring the current from said first arc path to said parallel arc path for the remainder of the conducting period.

3. An improved electric valve comprising two pairs of parallel electrode elements, means for initiating a current carrying arc to one pair of parallel connected electrodes at the beginning of the conducting period, means for initiating a current carrying are between the other parallel pair of electrodes near the termination of the conducting period and means for transferring the current from the first arc to the parallel are for deionizing the first arc space before the termination of the current carrying period.

4. An electric valve having a plurality of arc paths said are paths being of different reluctance, means for initiating a current carrying arc in the path of higher reluctance at the beginning of the conducting cycle, means for initiating a current carrying arc in the path of lower reluctance near the end of the conducting cycle whereby the final current is carried in the path of lower reluctance.

5. An electric valve having a plurality of arc paths said are paths being of different reluctance, means for initiating a current carrying arc in the path of higher reluctance at the beginning of the conducting cycle, means for initiating a current carrying arc in the path of lower reluctance near the end of the conducting cycle whereby the final current is carried in the path of lower reluctance and means for interrupting current flow in said path of lower reluctance.

6. A valve element for a vapor electric converter comprising a main discharge device, a single anode and cathode in said main discharge device, an auxiliary discharge device having an anode and cathode connected to said main anode and cathode and means for transferring the final portion of the current carrying arc to said auxiliary discharge device whereby said main discharge device has a deionizing period prior to the application of inverse potential.

'7. An electric converter element comprising a main discharge device having a single anode and cathode, a make-alive electrode for initiating a current carrying arc in said main discharge device at the beginning of each conducting period, an auxiliary discharge device having a single anode and cathode, said auxiliary device being connected in parallel with said main discharge device, means for initiating a current carrying arc in said auxiliary device near the termination of the conducting period, said auxiliary device having a lower arc drop than the main discharge device.

LEON R. LUDWIG. 

